Drivers and their passengers are frequently exposed to the harmful pollutants and unpleasant odors of gasoline and diesel exhaust emissions. Levels of exhaust gases at major metropolitan intersections, in stop-and-go conditions, on congested freeways, in tunnels, or behind high-polluting vehicles, such as trucks or old cars, can be one hundred to one thousand times higher than concentrations of pollutants in the surrounding area. These pollutants include carbon monoxide (CO), hydrocarbons (HC), volatile organic compounds (VOC), nitrogen oxides (NOx), and so forth. Unfortunately, high concentrations of these gases tend to penetrate the vehicle interior through the ventilation system, and can compromise the health of individuals.
Some auto manufacturers are now incorporating sensors into their new luxury passenger vehicles to monitor outside air quality and prevent noxious gases from entering the vehicle interior thereby improving cabin air quality. For example, when noxious gases are detected, a controller controls airflow into the cabin, or passenger compartment, by controlling the source of the air to switch an inlet air valve from an outside air mode to a recirculation mode, in which the cabin air is recirculated through the ventilation unit.
A problem that occurs with automated positioning of the inlet air valve based on air quality sensing is that the ventilation unit can repeatedly cycle between the outside air and the recirculation modes, particularly when the vehicle is operated in congested city traffic. Each opening and closing of the air inlet valve changes the HVAC noise level in the vehicle cabin. This changing noise level can be annoying to the vehicle occupants, and can cause excessive wear on the air inlet valve and its corresponding components. Moreover, automated positioning prevents the vehicle occupants from being able to make tradeoffs between their desired cabin air quality and an acceptable amount of cycling between the outside air and the recirculation modes.
In addition, conventional sensor systems do not make the distinction between driving conditions that typically experience lower pollutant levels, i.e., relatively high speed highway and/or rural driving, and those that typically experience higher pollutant levels, i.e., lower speed city driving. It may be desirable to vary the sensitivity of the sensor system in response to varying driving conditions and pollutant levels to more efficiently control cycling between the outside air and the recirculation modes.
Unfortunately, however, a vast majority of new and pre-owned passenger vehicles are not equipped with any such sensors, notwithstanding their limitations. Thus, concerned individuals have no option but to manually switch between an outside air mode and a recirculation mode when they determine that pollutant levels of the outside air are undesirably high. Although a driver could switch to recirculation mode manually, the driver may forget to switch back to outside air mode. By remaining in the recirculation mode, the windows could fog or the carbon dioxide level could increase resulting in a decrease in the oxygen level. Fogged windows and/or a decreased oxygen level in the cabin could compromise the safety of the driver and his or her passengers.
Furthermore, some gaseous pollutants are undetectable by humans. Therefore, the individual may not realize that the pollutant level within the vehicle interior has become undesirably high, and that he or she should switch to recirculation mode. Even when gaseous pollutants are detectable, the pollutant level in the vehicle may have already become excessively high by time the individual is finally able to detect it. As such, manually switching to recirculation mode once noxious odors are detected may be disadvantageous since there is already a significant quantity of pollutants in the recirculated air.